Generally, S/R vehicles comprise three operational degrees of freedom. The first degree of freedom constitutes longitudinal movement along an aisle of a S/R facility whereby each vehicle accesses the position of each column of material stored along that aisle. Material is stored on shelving or the like in horizontally and vertically addressable arrays such that inventory is transported between the arrays and the S/R vehicle in a direction normal to the aisle. The second degree of freedom comprises operation of a shuttle which is mounted on a vertically driven carriage and moves normal to the material storing arrays whereby inventory is retrieved and stored along the aisle. The third degree of freedom comprises vertical drive for the carriage. This invention provides novel vertical drive apparatus and methods for the third degree of freedom.
Presently available S/R vehicles comprise vertical drive components which are individually mounted on the S/R vehicle structure. As such, the presently available vertical drive assemblies are assembled and tested only after the major S/R vertical drive assembly supporting components, which usually comprises an assembled vehicle, are available at a test or job site.
All S/R vehicles must conform to the clearance requirements of the aisle where used. Such requirements predefine a significant width limitation on allowable dimensions of S/R vehicles and parts assembled thereon. In the past, such limitations have led to the development of S/R vehicles which employ vertically mounting of large motors, and therefore, right angle speed reducers to translate vertical motor rotary motion in horizontal plan to a horizontal drum vertical rotary motion which winds and unwinds a vertically disposed lift cable.
Generally, S/R vehicles comprise a mounting frame, a motor mounted to the frame, and a drum assembly which raises and lowers the carriage by winding and unwinding at least one carriage supporting lift cable. A speed reducer is commonly used between the motor and drum to translate relatively high rotational speed of the motor to a lower rotating speed required of the cable winding and unwinding drum.
In the present art, these and two methods of mounting a motor relative to the position of the drum. The first method comprises mounting the drum directly to the speed reducer output shaft and, thereby, directly coupling the motor to the drum along a common axis. In-line connections among the motor, speed reducer, and drum, severely limit the collective and individual sizes of motors, reducers, and drums which may be used and yet stay within the above mentioned width limitation.
To solve problems provided by the first method, the second method, as mentioned above, comprises a vertically disposed and mounted motor and a right angle speed reducer to drive the horizontally disposed drum. A power translation device, capable of withstanding low speed, high torque, driving forces, is disposed between the speed reducer and drum.
The second method has improved space, orientation, and speed flexibility over the first method, but requires a chain be used as the power translation device to drive the drum at the site of maximum tension. Commonly, such use of chains requires frequent maintenance and constant lubrication. Further, chains most often use tensioners which push against the side of the chain to maintain proper tautness in the chain. There is no tensioning required in the first method.
Generally, the present art uses a brake mounted on the end of the motor. Such brakes are usually electrically released, spring actuated disc brakes. Such braking is ineffective when a chain breaks.